The present invention relates to a metal-working fluid. More particularly, the invention relates to a water soluble metal-working fluid, which can be used as a substitute for a cutting oil.
Cutting metals such as iron, aluminum, and various types of alloys is one of the metal-working processes for removing unnecessary parts from a metal workpiece with the use of a cutting tool, which is widely used for providing a desired shape, size or surface to the metal workpiece.
In many cases of metal cutting work, enormous friction between a workpiece and a tool causes various problems such as frictional heat and thermal expansion. The frictional heat burns the tool and makes the surface of the workpiece rough, and the thermal expansion lowers the accuracy of the shape and the size of the workpiece and the tool. To overcome these problems, a cutting fluid or a lubricant has been employed in metal cutting.
A water-soluble or water-insoluble cutting oil is commonly used as a cutting fluid or lubricant. A typical example of a water-insoluble cutting oil is an oil solution comprising mineral oil as a base and sulfur and chlorine as additives. The disadvantage of the oil solution is that it can be used only when the cutting temperature is low because high cutting temperature may cause the production of fire and smoke. A water-soluble cutting oil is, for example, prepared by adding soap and sulfate as an emulsifier and higher alcohol and fatty acid ester as a binder to mineral oil and the like. Such water-soluble cutting oil is generally used after being diluted with water. A water-soluble cutting oil has an excellent lubricity, but on the other hand, it has low cooling property.
Both water-insoluble and water-soluble cutting oils can be used repeatedly in cutting operation. However, the bacteria propagates in cutting oils as time goes by, and therefore the cutting oil gives off an offensive odor by the bacteria itself or the gas produced by the bacteria. The disposal of used cutting oil has become the serious problem because the mineral oil and emulsifier contained therein exerts a negative influence on the environment when the oil is discharged as a waste liquid.
The present invention provides an environment-friendly metal-working fluid having excellent lubricity and cooling properties.
The metal working fluid of the present invention is an aqueous solution comprising metal stearate, carbonate, hydrogencarbonate, and surfactant.
The metal working fluid of the present invention may further comprise ethyleneglycol.
In the metal working fluid of the present invention, the metal stearate may be sodium stearate.
In the metal working fluid of the present invention, the carbonate may be sodium carbonate.
In the metal working fluid of the present invention, the hydrogencarbonate may be sodium hydrogencarbonate.
The metal working fluid of the present invention may further comprise a rust inhibitor.
The rust inhibitor may be an aqueous solution containing saturated fatty acid, ethylene diamine tetraacetato (EDTA) complex, tryltriazole, benzotriazole, and hydroxide.
The term xe2x80x9cmetal workingxe2x80x9d used herein refers broadly to metal cutting such as cutting with an edge tool, turning, drilling, planning and milling, and grinding with abrasive grain such as honing and lapping. It is also not limited in use to metal working, but may be used in rock drilling or the like.
One of the objects of the present invention is to provide a metal working fluid having an excellent lubricity and cooling property, which is capable of being mainly used to cut metals, preventing abrasion of a cutting tool, and extending the service life of a tool.
Another object of the present invention is to provide a metal working fluid, which can be used a number of times and does not contain environmentally hazardous substances.
A metal working fluid comprising a metal stearate, carbonate, hydrogencarbonate, and surfactant according to the present invention may have a pH value in the range from 7.5 to 10 under atmospheric pressure.
The metal working fluid of the present invention is an aqueous solution prepared by dissolving at least a metal stearate, carbonate, hydrogencarbonate, and surfactant in distilled water, deionized water, or tap water having a melting point of about 0xc2x0 C., a boiling point of about 100xc2x0 C., and a density of about 1.00 g/cm3 at a temperature of 4xc2x0 C.
The metal working fluid of the present invention may be prepared by further adding ethyleneglycol thereto. Although the metal stearate content, carbonate content, hydrogencarbonate content, surfactant content, and ethyleneglycol content are not particularly limited, the metal working fluid of the present invention preferably contains 0.05 to 0.5 wt % of metal stearate, 0.1 to 1 wt % of carbonate, 0.05 to 0.5 wt % of hydrogencarbonate, 0.1 to 2 wt % of ethyleneglycol, and 0.05 to 0.2 wt % of surfactant.
The metal stearate contained in the metal working fluid of the present invention is not particularly limited, but any metal stearate known to persons skilled in the art can be used. Examples of a preferable metal stearate are an alkali metal stearate such as lithium stearate, sodium stearate, potassium stearate, or rubidium stearate. The most preferable stearate is either sodium stearate or potassium stearate.
The carbonate contained in the metal working fluid of the present invention is not particularly limited, but any carbonate known to persons skilled in the art can be used. Examples of carbonate include potassium carbonate, calcium carbonate, and sodium carbonate. A preferable carbonate can be either sodium carbonate or potassium carbonate.
The hydrogencarbonate contained in the metal working fluid of the present invention is not particularly limited, but any hydrogencarbonate known to persons skilled in the art can be used. Examples of hydrogencarbonate used herein include potassium hydrogencarbonate, calcium hydrogencarbonate, and sodium hydrogencarbonate. A preferable hydrogencarbonate can be either sodium hydrogencarbonate or potassium hydrogencarbonate.
The surfactant contained in the metal working fluid of the present invention is not particularly limited, but any surfactant known to persons skilled in the art can be used.
The metal working fluid containing metal stearate, carbonate, hydrogencarbonate, surfactant, and ethyleneglycol can be used as a substitute for a conventional cutting oil. However, if the metal working fluid is left on them, a cutting tool and a workpiece can often be rusted. Therefore, a metal working fluid preferably contains a rust inhibitor. The rust inhibitor is not particularly limited, but any rust inhibitors known to persons skilled in the art can be used. Examples of the rust inhibitors include an ion coat type agent, paraffin wax, and carnauba wax. Preferably, a non-amine rust inhibitor is used to prepare a metal working fluid which does not adversely affect the environment. Examples of the non-amine rust inhibitor are aqueous solutions containing BTA (benzotriazole), TTA (thenoyltrifluoroacetone), methylbenzotriazole, and the like. A metal working fluid may further contain saturated fatty acid, dibasic acid, hydroxide, and EDTA complex to enhance rust-preventive effect. Examples of saturated fatty acid include caproic acid, caprylic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, and stearic acid, and thus any saturated fatty acid known to persons skilled in the art can be used. Examples of the dibasic acid salt include dodecanoic diacid and sebacic acid.
In addition, a metal working fluid of the present invention may further contain a pH adjuster and a pH stabilizer.
Examples of a cutting tool to be used in metal cutting with a metal working fluid of the present invention include single-point tools such as a bite, multiple-point tools such as a drill, reamer, milling cutter, broach, saw and shank, and formed tool whose cutting edge is the same shape as a specific outline of a product. Examples of materials of a cutting tool include carbon tool steel, high-speed steel, cast nonferrous alloys, sintered carbides, sintered oxides, diamonds, artificial grindstone and the like.
Examples of a workpiece to be cut using a metal working fluid of the present invention include bar steels such as a round bar, a square bar and a hexagonal bar steel, and steel plates. More specifically, examples of the workpiece include a structural rolled steel for welding, a carbon steel, a molybdenum steel plate, a round bar for rivet, a round bar for chain, a rolled steel for welding, a carbon steel tube for machine structural use, but the workpiece to be cut is not limited by the above.
A metal working fluid of the present invention can prevent heat damage to a cutting tool, destruction of a cutting blade, and increasing abrasion of a cutting blade.
For example, a metal working fluid of the present invention may be supplied to a pump of a circular sawing machine, a bench drilling machine, a turning machine, or the like and can be used to cut and drill a round bar and to produce a flange surface.
The metal working fluid of the present invention has a lower viscosity than conventional cutting oils, so that smooth liquid flow and excellent circulation in a pump can be insured. Moreover, a metal working fluid of the present invention has an excellent lubricity and cooling property, which can prevent frictional heat from being produced between a tool and a workpiece, so that the effective tool life can be increased. In addition, the metal working fluid of the present invention can prevent bite traces from being left on the flange surface of a workpiece, so that the workpiece is finished nicely in appearance.